The mapcspace driver reads a occupancy grid map from another map device and convolves it with a robot of a particular shape and size to create the configuration space (C-space) map. That is, this driver "grows" obstacles in the map to produce a new map in which, for path-planning purposes, you can consider the robot to be a point.

Both occupied and unknown cells are grown.

Note that map devices produce no data; the map is delivered via a sequence of configuration requests.